IBM 3270

(hardware)A class of terminals made by IBM known as"Display Devices", normally used to talk to IBMmainframes. The 3270 attempts to minimise the number ofI/O interrupts required by accepting large blocks of data,known as datastreams, in which both text and control (orformatting functions) are interspersed allowing an entirescreen to be "painted" as a single output operation. Theconcept of "formatting" in these devices allows the screen tobe divided into clusters of contiguous character cells forwhich numerous attributes (color, highlighting, character set, protection from modification) can be set. Further,using a technique known as 'Read Modified' the changes fromany number of formatted fields that have been modified can beread as a single input without transferring any other data,another technique to enhance the terminal throughput of theCPU.

The 3270 had twelve, and later twenty-four, special ProgrammedFunction Keys, or PF keys. When one of these keys waspressed, it would cause the device to generate an I/Ointerrupt and present a special code identifying which keywas pressed. Application program functions such astermination, page-up, page-down or help could be invoked by asingle key-push, thereby reducing the load on very busyprocessors.

A version of the IBM PC called the "3270 PC" was released inOctober 1983. It included 3270 terminal emulation.

tn3270 is modified version of Telnet which acts as a 3270terminal emulator and can be used to connect to an IBMcomputer over a network.

See also broken arrow.

单词	ibm 3270
释义	IBM 3270 IBM 3270 (hardware)A class of terminals made by IBM known as"Display Devices", normally used to talk to IBMmainframes. The 3270 attempts to minimise the number ofI/O interrupts required by accepting large blocks of data,known as datastreams, in which both text and control (orformatting functions) are interspersed allowing an entirescreen to be "painted" as a single output operation. Theconcept of "formatting" in these devices allows the screen tobe divided into clusters of contiguous character cells forwhich numerous attributes (color, highlighting, character set, protection from modification) can be set. Further,using a technique known as 'Read Modified' the changes fromany number of formatted fields that have been modified can beread as a single input without transferring any other data,another technique to enhance the terminal throughput of theCPU. The 3270 had twelve, and later twenty-four, special ProgrammedFunction Keys, or PF keys. When one of these keys waspressed, it would cause the device to generate an I/Ointerrupt and present a special code identifying which keywas pressed. Application program functions such astermination, page-up, page-down or help could be invoked by asingle key-push, thereby reducing the load on very busyprocessors. A version of the IBM PC called the "3270 PC" was released inOctober 1983. It included 3270 terminal emulation. tn3270 is modified version of Telnet which acts as a 3270terminal emulator and can be used to connect to an IBMcomputer over a network. See also broken arrow.
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